Reverse flow valve for fuel injectors

ABSTRACT

A reverse flow valve member is positioned within an injector body of a fuel injector and is movable between a closed position and an open position. When the reverse flow valve member is in its closed position, an upper portion of a nozzle supply passage is blocked from fluid communication with a lower portion of the nozzle supply passage. A compressed spring biases the reverse flow valve member to its closed position. When the reverse flow valve member is in its open position, the fuel pressurization chamber is fluidly connected to the lower portion of the nozzle supply passage. The present invention limits gas ingestion due to tip leakage, and allows an injector with trapped gas to prime itself.

TECHNICAL FIELD

[0001] This invention relates generally to fuel injectors, and morespecifically to reverse flow check valves within fuel injectors.

BACKGROUND

[0002] Occasionally, an injector nozzle of a fuel injector will becomeleaky, and after an injection event, allow hot combustion gases from theengine cylinder to leak past the nozzle outlet and travel upwards intothe nozzle supply passage of the fuel injector. If the gases arepermitted to continue to travel upwards and reach the fuelpressurization chamber, the fuel injector will inject less than apredicted amount of fuel, and can eventually be unable to pressurizefuel and inject it into the engine cylinder.

[0003] Typically, gases have been blocked from the fuel pressurizationchamber by reverse flow check valve assemblies having a variety ofstructures. One example of such a check valve assembly is shown inco-owned U.S. Pat. No. 5,287,838 issued to Wells on Feb. 22, 1994. Thefunction of the check valve assembly is to permit communication of highpressure fuel from the fuel pressurization chamber to the nozzle outletof the fuel injector during an injection phase, but to preventcommunication (i.e., reverse flow) of engine cylinder combustion gasfrom the nozzle to the fuel pressurization chamber at the end of aninjection event and during a non-injection phase if the nozzle of thefuel injector becomes leaky.

[0004] Referring to FIG. 1, there is shown a partial sectioned sidediagrammatic view of a fuel injector 10 according to the aboveidentified patent. The fuel injector 10 consists of an injector body 11that includes a barrel 33 separated from a stop component 42 by arelatively thin plate 50. A plunger 13 is movably positioned along acenterline 12 within the injector body 11. The plunger 13, the barrel 33and the plate 50 define a fuel pressurization chamber 14 that is fluidlyconnected to a fuel tank (not shown) via a fuel supply line 30. When theplunger 13 is driven downward, it advances along the centerline 12 inorder to pressurize fuel delivered from the fuel tank (not shown) viathe fuel supply line 30. A check valve 32 is positioned within the fuelsupply line 30. The check valve 32 is in its closed position in which itblocks fluid communication between the fuel pressurization chamber 14and the fuel supply line 30 when the plunger 13 is advancing downwardand increasing the pressure within the fuel pressurization chamber 14.When the plunger 13 is returning to its upward position, the pressurewithin the pressurization chamber 14 decreases such that the check valve32 opens and low pressure fuel within the fuel supply line 30 can flowpast the check valve 32 and into the fuel pressurization chamber 14.

[0005] The injector body 11 defines a nozzle supply passage 15, a nozzleoutlet 17, and a guide bore 54. A needle valve is positioned in theinjector body 11 and has a needle valve member 20 that is movablebetween a first position, in which the nozzle outlet 17 is open, and asecond position, in which the nozzle outlet 17 is closed. The needlevalve member 20 has an opening hydraulic surface 21 that is exposed tofluid pressure within the nozzle supply passage 15, but is biased towarda closed position by a compressed spring 22. When the needle valvemember 20 is in its open position, a stop surface of the needle valvemember 20 is in contact with the stop component 42, and the nozzleoutlet 17 is opened to allow pressurized fuel to be injected into theengine cylinder (not shown).

[0006] The fuel pressurization chamber 14 is fluidly connected to thenozzle outlet 17 via the nozzle supply passage 15, which includes theguide bore 54. Positioned within the guide bore 54, there is a reverseflow check valve assembly that includes a reverse flow check 52, theplate 50, and the stop component 42. The reverse flow check 52 ispreferably a flat circular plate and defines a flow passage 53. The flowpassage 53 is preferably cylindrical and centrally positioned within thereverse flow check 52 and is fluidly connected to the nozzle supplypassage 15. The plate 50, which is preferably flat, is positionedbetween the barrel 33 and the stop component 42 and defines a pair ofkidney-shaped or crescent-shaped holes 51, which are fluidly connectedto the fuel pressurization chamber 14. The flow passage 53 of thereverse flow check 52 is radially inwardly spaced from the kidney holes51 of the plate 50 and is arranged so that the nozzle supply passage 15is blocked from the pressurization chamber 14 when the reverse flowcheck 52 and the plate 50 are in contact. The reverse flow check 52 ismovable between an open position and closed position. When in its openposition, as shown, the reverse flow check 52 is in contact with thestop component 42, and the fuel pressurization chamber 14 is fluidlyconnected to the nozzle supply passage 15 via the kidney holes 51 of theplate 50 and the flow passage 53 of the reverse flow check 52.

[0007] Prior to an injection event, the plunger 13 is driven downward bya hydraulic intensifier piston or a tappet along a centerline 12 of thefuel injector 10 toward its downward position. This greatly increasesthe pressure within the upper portion of the nozzle supply passage 15which includes the fuel pressurization chamber 14 and the lower portionof the nozzle supply passage 15. The increased pressure within the fuelpressurization chamber 14 will also close the check valve 32, blockingfluid communication between the fuel pressurization chamber 14 and thefuel tank (not shown) via the fuel supply line 30. The reverse flowcheck 52 will be in its first, or open, position, and in contact withthe stop component 42. Thus, the pressurized fuel will flow from thefuel pressurization chamber 14 through kidney holes 51 within the plate50 and through the flow passage 53 of the reverse flow check 52 to thelower portion of the nozzle supply passage 15. Thus, during an injectionevent, the fuel pressurization chamber 14 is fluid connected to thelower portion of the nozzle supply passage 15.

[0008] Shortly before the desired amount of pressurized fuel is injectedinto the engine cylinder via the nozzle outlet 17 of the fuel injector10, the plunger 13 will stop moving downward, resulting in a fuelpressure drop to below valve closing pressure. This causes the needlevalve member 20 to move to its closed position under the action ofspring 22. Towards the end of the movement of the needle valve member 20to its closed position, there is a reverse flow of pressurized fuelwithin the lower portion of the nozzle supply passage 15. The reverseflow of fuel will lift the reverse flow check 52 out of contact with thestop component 42. The reverse flow check 52 will be lifted upward untilit is in contact with the plate 50 and, thus, in its second, or closed,position. Due to the positioning and placement of the kidney holes 51 ofthe plate 50 and the flow passage 53 of the reverse flow check 52, fluidcommunication between the fuel pressurization chamber 14 and the nozzlesupply passage 15 will be blocked. Gas ingestion can occur over a briefinstant as the needle valve member 20 is not yet closed while fuelpressure has dropped below cylinder pressure. If any engine cylindercombustion gases enter through the nozzle outlet 17 into the lowerportion of the nozzle supply passage 15, they will be blocked from fluidcommunication with the fuel pressurization chamber 14 when the reverseflow check 52 is in its closed position. Thus, the prior injectorprevents gas from being trapped within the fuel pressurization chamber14 by utilizing the reverse flow check 52, the plate 51, and the stopcomponent 42.

[0009] The hydraulic pressure acting on the plunger 13 is then reducedallowing the plunger 13 to retract along the centerline 12 to its upwardposition under the action of its biasing spring 16. As the plunger 13retracts, the pressure within the fuel pressurization chamber 14preferably will lessen such that fuel from the fuel tank (not shown) canbe drawn into the fuel pressurization chamber 14 via the fuel supplyline 30 past the check valve 32. The injection process can once againbegin.

[0010] Although these reverse flow check valve assemblies have performedwell, there is room for improvement. For instance, the reverse flowcheck valve assemblies limit combustion gases from leaking into the fuelpressurization chamber 14 through the nozzle outlet 17 by blocking fluidcommunication between the lower portion of the nozzle supply passage 15and the fuel pressurization chamber 14 toward the end of an injectionevent. However, the reverse check valve assemblies do not prevent allgases ingested through the nozzle outlet 17 from traveling to the fuelpressurization chamber 14. Because the reverse flow check 52 remains inthe closed position only for a limited time when the reverse flow offuel is hydraulically displacing it, there is the possibility thatcombustion gases can leak past the nozzle outlet 17 after the hydraulicpressure caused by the reverse flow of fuel within the nozzle supplypassage has subsided. This can occur due to excessive wear on the needlevalve seat. Further, the reverse control valve assembly cannot preventgases from leaking into the fuel pressurization chambers 14 by othermeans than gas ingestion through the nozzle outlet 17. Theoretically,gas trapping may occur if t hot combustion gases leak past seals on theouter surface of the fuel injector 10 and travel upward along the outersurface of the fuel injector 10 until they reach the area in the enginehead where the fuel supply line 30 exists. The gases then mix with thelow pressure fuel and are delivered to the fuel pressurization chamber14.

[0011] Occasionally, hot combustion gases are ingested through theinjector tip and/or enter via the fuel supply are trapped within thefuel pressurization chamber 14 and the nozzle supply passage 15 by thecheck valve 32 and the direct needle control valve member 20. Thetrapped gas creates pressure within the fuel pressurization chamber 14sufficient to prohibit the check valve 32 from rising off its seat andallowing low pressure fuel into the fuel pressurization chamber 14.Thus, the fuel pressurization chamber 14 is blocked from fluidcommunication with the fuel supply line 30 by the check valve 32. Thepressure caused by the trapped gas acting on the opening hydraulicsurface 21 within the nozzle supply passage 15 is sometimes not greatenough to overcome the biasing spring 22 of the needle valve member 20.Thus, the nozzle supply passage 15, is blocked from fluid communicationwith the nozzle outlet 17. When this gas trapping occurs, the plunger 13will advance downward to pressurize the fuel, but there will be littleor no fuel within the fuel pressurization chamber 14 because the fuelpressurization chamber 14 is blocked from the fuel supply line 30 by theclosed check valve 32. The gas can never reach a high enough pressure toopen the needle valve member 20 and the gas pressure never drops lowenough to allow the check valve 32 to lift to its open position to allowfuel into the fuel pressurization chamber 14. Thus, the plunger 13reciprocates up and down but nothing happens with the fuel injector 10.In these cases, the fuel injector 10 needs a means for re-primingitself.

[0012] Also, during assembly of new fuel injectors 10, gases, other thanengine cylinder gases, can be trapped within the empty space within thefuel pressurization chambers 14. If the gas trapping occurs in a newfuel injector 10, the fuel injector 10 is unable to prime itself andinject fuel into the engine cylinder. If the gas trapping occurs duringoperation of a fuel injector 10, the fuel injector 10 is unable tore-prime itself by pushing the gases out of the nozzle outlet 17. Ineither situation, once gases are in the fuel pressurization chamber 14,the pressure within the nozzle supply passage 15 will be insufficient toopen the nozzle outlet 17 and the pressure within the fuelpressurization chamber 14 will be too great for the check valve 32 toopen. Thus, because the fuel injector 10 has no way of pushing the gaspressure out of the fuel pressurization chamber 14, the plunger 13 willreciprocate up and down and nothing will happen within the fuel injector10.

[0013] Moreover, the plate 50 used as a stop for the reverse flow check52 is subject to fretting, and the thin plate decreases the availableheight of the stop component 42 which in return increases the risk ofoil to fuel transfer.

[0014] The present invention is directed to overcoming one or more ofthe problems set forth above.

SUMMARY OF THE INVENTION

[0015] In one aspect of the invention, a fuel injector comprises aninjector body that defines a nozzle supply passage and a nozzle outlet.Within the injector body is positioned a reverse flow valve member thathas an opening hydraulic surface exposed to fluid pressure in an upperportion of the nozzle supply passage. The reverse flow valve member ismoveable between a closed position in which the nozzle supply passage isblocked and an open position in which the nozzle supply passage is open.The reverse flow valve member is biased toward the closed positioned bya compressed spring.

[0016] In another aspect, a fuel injector includes an injector bodydefining a nozzle outlet. The injector body also includes a barrel thatis in contact with a stop component. A movable plunger is at leastpartially positioned in the barrel. A reverse flow valve member istrapped between the barrel and the stop component, and is movablebetween a first position and a second position. The plunger, the reverseflow valve member, and the injector body define a nozzle supply passagethat includes a fuel pressurization chamber. When the reverse flow valvemember is in the second position, the nozzle supply passage is fluidlyconnected to a lower portion of the nozzle supply passage. A compressedspring is operably positioned in the injector body to bias the reverseflow valve member toward the first position, in which the fuelpressurization chamber is blocked from the lower portion of the nozzlesupply passage.

[0017] In still another aspect, gas ingestion in a fuel injector isreduced by moving a reverse flow valve member at least in part with aspring to a position that blocks a downstream portion of a nozzle supplypassage to an upstream portion of the nozzle supply passage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a partial sectioned side diagrammatic view of a fuelinjector according to the prior art;

[0019]FIG. 2 is a partial sectioned side diagrammatic view of a fuelinjector according to the preferred embodiment of the present invention;

[0020]FIG. 3 is an enlarged view of the reverse flow valve memberpositioned within the fuel injector of FIG. 2;

[0021]FIG. 4 is a top view of the reverse flow valve member shown inFIG. 3 and FIG. 2;

[0022]FIG. 5 is a partial sectioned side diagrammatic view of a reverseflow valve member positioned within a fuel injector according to analternative embodiment of the present invention;

[0023]FIG. 6 is a top view of the reverse flow valve member shown inFIG. 5;

[0024]FIG. 7 is a partial sectioned side diagrammatic view of a reverseflow valve member positioned within a fuel injector according to asecond alternative embodiment of the present invention; and

[0025]FIG. 8 is a front view of the reverse flow valve member shown inFIG. 7.

DETAILED DESCRIPTION

[0026] Referring to FIG. 2, there is shown a partial sectioned sidediagrammatic view through a fuel injector 110 according to the presentinvention. The fuel injector 110 includes an injector body 111 thatincludes a barrel 133 and a stop component 142. Features of fuelinjector 110 that are identical to those described with respect to fuelinjector 10 of FIG. 1 have identical numbering. A plunger 13 is movablypositioned along a centerline 12 within the injector body 111. While theplunger 13, the barrel 33 and a thin plate 50 define a pressurizationchamber 14 according to the prior art as illustrated in FIG. 1, theinjector body 111, the plunger 13, and a reverse flow valve member 160define a nozzle supply passage 115 that includes a fuel pressurizationchamber 114 according to the present invention as illustrated in FIG. 2.The fuel pressurization chamber 114 is fluidly connected to a fuel tank(not shown) via a fuel supply line 130. When plunger 13 ishydraulically-activated, it advances downward along the centerline 12 inorder to pressurize fuel delivered from the fuel tank (not shown) viathe fuel supply line 130. A check valve 32 is positioned within the fuelsupply line 130. The check valve 32 is in its closed position in whichit blocks fluid communication between the fuel pressurization chamber114 and the fuel supply line 130 when the plunger 13 is advancingdownward and increasing the pressure within the pressurization chamber114. When the plunger 13 is returning to its upward position, thepressure within the pressurization chamber 114 decreases such that thecheck valve 32 opens and low pressure fuel within the fuel supply line130 can flow past the check valve 32 and into the pressurization chamber114.

[0027] The injector body 111 defines a nozzle outlet 17 and a nozzlesupply passage 115, which includes a guide bore 154. A direct controlneedle valve is positioned in the injector body 11 and has a directcontrol needle valve member 20 that is movable between a first position,in which the nozzle outlet 17 is open, and a second position, in whichthe nozzle outlet 17 is closed. When the direct control needle valvemember 20 is in the second, or open, position, the direct control needlevalve member 20 is in contact with the stop component 142. The directcontrol needle valve member 20 has an opening hydraulic surface 21 thatis exposed to fluid pressure within the nozzle supply passage 115 and aclosing hydraulic surface 23 that is exposed to fluid pressure within aneedle control chamber 24. A pressure communication passage 25 is influid communication with the needle control chamber 24 and controlsfluid pressure within the same. The closing hydraulic surface 23 and theopening hydraulic surface 21 are preferably sized such that even when avalve opening pressure is attained in the nozzle supply passage 115, thedirect control needle valve member 20 will not lift open when the needlecontrol chamber 24 is fluidly connected to a source of high pressureactuation fluid. However, it should be appreciated that the relativesizes of the closing hydraulic surface 23 and the opening hydraulicsurface 21 should be such that when the closing hydraulic surface 23 isexposed to low pressure in the needle control chamber 24, the highpressure fuel acting on the opening hydraulic surface 21 should besufficient to move the direct control needle valve member 20 upwardagainst the force of its biasing spring 22 to open the nozzle outlet 17.Those skilled in the art should appreciate that while direct controlneedle valve is the preferred method of controlling the nozzle outlet17, a nozzle outlet valve solely controlled by the biasing spring 22 andthe hydraulic pressure within the nozzle supply passage 115 may also beused in the present invention.

[0028] The injector body 111, the plunger 13, and a reverse flow valvemember 160 define the nozzle supply passage 115, which includes the fuelpressurization chamber 114. Although the described fuel injector 110includes a fuel pressurization chamber 114, those skilled in the artwill appreciate that the present invention could be utilized in a commonrail fuel injector in which there is no fuel pressurization chamber.Rather than the plate 50 being positioned between the barrel 33 and thestop component 42 as it is in the fuel injector 10 according to theprior art, a barrel 133 and a stop component 142 are in contact in thefuel injector 110 according to the present invention. It should also beappreciated that, by removing the plate 50, the height of the stopcomponent 142 can be increased, which should reduce the oil to fueltransfer and prevent fretting that sometimes occurs in plate 50.Further, by removing the plate 50 from the present invention, the platebreakage that could occur over time is no longer a concern. A reverseflow valve member 160 is positioned within the guide bore 154 and istrapped between the barrel 133 and the stop component 142. Although itcould be positioned at any point along the nozzle supply passage 115,the reverse flow valve member 160 preferably is positioned as close tothe plunger 13 as possible so that the reverse flow valve member 160 canaid in priming a new fuel injector 110 in the event gas is trappedwithin its fuel pressurization chamber 114 upon assembly. The reverseflow valve member 160 member is movably positioned along a line parallelto and offset a distance, from the centerline 12 of the injector body111. The reverse flow valve member 160 is movable between a firstposition, or closed position, in which the lower portion of the nozzlesupply passage 115 is blocked from fluid communication with the fuelpressurization chamber 114, and a second position, or open position, inwhich the lower portion of the nozzle supply passage 115 is open tofluid communication with the fuel pressurization chamber 114. Thereverse flow valve member 160 is biased to its first position by acompressed spring 161 operably positioned in the injector body

[0029] Referring to FIG. 3 and FIG. 4, there is shown an enlarged viewand a top view of the reverse flow valve member 160 of FIG. 2,respectively. In the preferred embodiment, the reverse flow valve member160 has a cupped shape and defines a hollow interior in which acompressed spring 161 is operably positioned to bias the reverse flowvalve member 160 toward its upward, closed position. The reverse flowvalve member 160 has an opening hydraulic surface 164 exposed to fluidpressure within the fuel pressurization chamber 114 that is part of theupstream portion of the nozzle supply passage 115. When the plunger 13advances downward to pressurize fuel within the fuel pressurizationchamber 114, the increased pressure within the fuel pressurizationchamber 114 acting on the opening hydraulic surface 164 moves thereverse flow valve member 160 against the action of its compressedspring 161 to its open position in which it is not in contact with aflat valve seat 163 of the barrel 133. In its open position or itssecond position, as shown, the reverse flow valve member 160 defines agroove 153 that fluidly connects the fuel pressurization chamber 114that is included in the upper portion of the nozzle supply passage 115to the lower portion of the nozzle supply passage 115. Toward the end ofan injection event, the decreased pressure acting on the openinghydraulic surface 163 permits the reverse flow valve member 160 toreturn in its closed, or first, position, in which the reverse flowvalve member 160 is in contact with the flat valve seat 163 of thebarrel 133 and, thus, blocks fluid communication between the fuelpressurization chamber 114 and the nozzle supply passage 115, and viceversa. The size of the groove 153 is preferably selected such that it islarge enough to communicate a portion of the required fuel to flow pastthe reverse flow valve member 160 during an injection event but smallenough that there is no leakage between the reverse flow valve member160 and the valve seat 163 of the barrel 133 during a non injectionperiod.

[0030] While the prior art solely relied on of the pressure gradientbetween the fuel pressurization chamber 14 and the lower portion or thenozzle supply passage 15 to control the movement of the reverse flowcheck 52, the present invention uses the compressed spring 161positioned underneath the reverse flow valve member 160 and the pressurewithin the fuel pressurization chamber 114 to control the movement ofthe reverse flow valve member 160. The strength of the compressed spring161 is great enough that the reverse flow valve member 160 will remainin its first position for a time sufficient to prevent gas ingestioninto the fuel pressurization chamber 114 during peak cylinder pressure.However, the strength of the compressed spring 161 is limited such thatthe reverse flow valve member 160 remains in its second position for atime sufficient to allow pressurized fuel to flow into the nozzle supplypassage 115 before the next injection event. The present inventionallows for better control over the movement of the reverse flow valvemember 160, which helps prevent fuel leakage into the engine cylinder.In the preferred embodiment, a pin 162 is operably positioned within theguide bore 154 between the reverse flow valve member 160 and the stopcomponent 142. Because the pin 162 is received in the guide bore 154 andinto the stop component 142, the pin 162 prevents the reverse flow valvemember 160 from rotating with respect to the injector body 111.

[0031] Referring to FIG. 5 and FIG. 6, there is shown a partialsectioned side diagrammatic view and a front view of a reverse flowvalve member 260 according to an alternate embodiment of the presentinvention, respectively. Similarly as the preferred embodiment of thepresent invention, the reverse flow valve member 260 is trapped betweena stop component 242 and a barrel 233 and is movable between a firstposition, or a closed position, and a second position, or an openposition. The difference between the fuel injector 110 of the preferredembodiment and the fuel injector 210 of the alternate version is theshape of the reverse flow valve members 160, 260. Rather than having acupped-shape and a hollow interior as does the reverse flow valve member160 of the preferred embodiment, the reverse flow valve member 260 is asolid disc under which a compressed spring 261 is positioned. Just as inthe preferred embodiment, a pin 262 is operably positioned within aguide bore 254 between the reverse flow valve member 260 and the stopcomponent 242 so to prevent the reverse flow valve member 260 fromrotating with respect to its injector body 211.

[0032] Referring to FIG. 7 and FIG. 8, there is shown a partialsectioned side diagrammatic view and a front view of a reverse flowvalve member 360 according to a second alternate embodiment of thepresent invention, respectively. The second alternate embodiment workssimilar to the preferred embodiment of the present invention except forthe shape of a reverse control flow valve member 360, the shape of avalve seat 364 and the interaction between the reverse flow valve member360 and its injector body 311. Rather than having a circular shape, thereverse flow valve member 360 is rectangular. Because the reverse flowvalve member 360 is solid, a compressed spring 361 is operablypositioned below the reverse flow valve member 360 in order to bias thereverse flow valve member 360 to its closed position. Further, a valveseat 363 of a barrel 333 is flat and slanted rather than flat andhorizontal like in the other embodiments of the present invention.Because the reverse flow valve member 360 and a guide bore 354 arerectangular, there is no need for a pin to prevent the reverse flowvalve member 360 from rotating.

[0033] Industrial Applicability

[0034] Referring to FIG. 2, operation of the present invention will bediscussed for fuel injectors that pressurize fuel within their injectorbodies. It should be appreciated that the present invention can operatein common rail fuel injectors in which the fuel is pressurized outsidethe body of the fuel injectors. Moreover, it should be appreciated thatwhile different fuel injectors within the engine operate at differentstages, the present invention operates in the same manner for each fuelinjector and can be applied in an engine with any number of fuelinjectors.

[0035] In the present invention, the plunger 13 is biased to its upwardposition under the action of its biasing spring 16. When plunger 13 isin its upward position, the pressure within the upper portion of thenozzle supply passage 115 that includes the fuel pressurization chamber114 is at relatively low fuel supply pressure and, thus, permits thecheck valve 32 to open and low pressure fuel to flow from the fuel tank(not shown) to the fuel pressurization chamber 114 via the fuel supplyline 130. When the plunger 13 is in its upward position, the pressurewithin the lower portion of the nozzle supply passage 115 acting on theopening hydraulic surface 21 of the direct control needle valve member20 is also low. Thus, the direct control needle valve member 20 willremain in its closed position under the action of its biasing spring 22and the hydraulic pressure within the direct control chamber 24,blocking fluid communication between the nozzle outlet 17 and the fuelpressurization chamber 114.

[0036] Prior to an injection event, the plunger 13 is driven downward bya hydraulic intensifier piston or a tappet to move along a centerline 12of the fuel injector 110 toward its downward position. This greatlyincreases fuel pressure within the upper portion of the nozzle supplypassage 115 which includes the fuel pressurization chamber 114 and thelower portion of the nozzle supply passage 115. The increased pressurewithin the fuel pressurization chamber 114 will close the check valve32, blocking fluid communication between the fuel pressurization chamber114 and the fuel tank (not shown) via the fuel supply line 130. Thepressurized fuel will act on the opening hydraulic surface 164 of thereverse flow valve member 160 and move the reverse flow valve member 160downward against the action of the compressed spring 161 to its second,or open, position. The reverse flow valve member 160 will move out ofcontact with the valve seat 163 of the barrel 133 so that thepressurized fuel can flow through to the lower portion of the nozzlesupply passage 115 via the groove 153 defined by the reverse flow valvemember 160 when in its second position. The direct control needle valvemember 20 remains in its closed position blocking fluid communicationbetween the nozzle outlet 17 and the nozzle supply passage 115 until thepressurized fuel acting on the opening hydraulic surface 21 of thedirect control needle valve member 20 reaches a valve opening pressuresufficient to overcome the bias of the biasing spring 22 and the needlecontrol chamber 24 is connected to low pressure via the pressurecommunication line 25. When the direct control needle valve member 20moves to its open position, a stop surface of the nozzle outlet valvemember 20 is in contact with the stop component 142, and the nozzleoutlet 17 is opened to allow pressurized fuel to be injected into theengine cylinder (not shown).

[0037] Shortly before the desired amount of pressurized fuel is injectedinto the engine cylinder via the nozzle outlet 17 of the fuel injector110, the pressure communication line 25 will connect the needle controlchamber 24 with a source of high pressure actuation fluid. The directcontrol needle valve member 20 will close under the hydraulic forcewithin the needle control chamber 24 and the bias of its spring 22. Inits closed position, the direct control needle valve member 20 isblocking fluid communication between the nozzle outlet 17 and the nozzlesupply passage 115. Those skilled in the art should appreciate that thedirect needle control valve is the preferred method for operating thenozzle outlet 17. The direct needle control valve allows the nozzleoutlet 17 to be closed under high pressure within the needle controlchamber 24 even when there is high pressure within the nozzle supplypassage 115. Thus, the nozzle outlet 17 can remain blocked despite thepressure within the nozzle supply passage 115. Although a nozzle outletvalve that is controlled solely by a biasing spring and 4 the pressurewithin the nozzle supply passage 115 can be used, the timing of thereverse flow valve member 160 can be important. When a nozzle outletvalve is used, if the reverse flow valve member 160 moves too quickly toits closed position, gases will be trapped within the nozzle supplypassage 115 causing pressure on the hydraulic surface 21 of the nozzlevalve outlet member such that it slows the closing of nozzle outlet 17.Fuel will be able to leak past the open nozzle outlet 17 and dribbleinto the engine cylinder causing smoke from the engine. If the reverseflow valve member 160 moves too slowly into its closed position, thenthe nozzle outlet 17 will close approximately at the same time as thereverse flow valve member 160 moves to its closed position. Thus, if thepressure within the engine cylinder is greater than the pressure withinthe nozzle supply passage 115 at the time the nozzle outlet 17 closes,some of the combustion gases will enter into the injector tip.

[0038] The hydraulic pressure acting on the plunger 13 is then reducedallowing the plunger 13 to retract along the centerline 12 to its upwardposition under the action of its biasing spring 16, causing the pressurewithin the fuel pressurization chamber 114 to decrease. The decreasedpressure within the fuel pressurization chamber 114 acting on theopening hydraulic surface 164 of the reverse flow valve member 160 willbe insufficient to overcome the action of the compressed spring 161.Thus, the reverse flow valve member 160 will move to its first, orclosed position, under the action of the compressed spring 161. When inthe first position, the reverse flow valve member 160 is in contact witha valve seat 163 of the barrel 133 and is blocking fluid communicationbetween the fuel pressurization chamber 114 and the lower portion of thenozzle supply passage 115. In the event of gas ingestion through the tipof the fuel injector 110, the gases moving up the lower portion of thenozzle supply passage 115 will be blocked from the fuel pressurizationchamber 114 by the reverse flow valve member 160, which is preferablyalready in its closed position due to the low pressure within the fuelpressurization chamber 114 acting on its opening hydraulic surface 164.Thus, the present invention blocks fluid communication between the fuelpressurization chamber 114 and the lower portion of the nozzle supplypassage 115 during a non-injection event. This limits gas ingestion dueto tip leakage to the relatively small volume below the reverse flowcontrol valve member 160.

[0039] Recall that, with the prior art, gases occasionally are trappedwithin the fuel pressurization chamber 14 and the nozzle supply passage15 by the check valve 32 and the direct control needle valve member 20.The trapped gas creates pressure within the fuel pressurization chamber14 sufficient to prohibit the check valve 32 from rising off its seatand allowing low pressure fuel into the fuel pressurization chamber 14.Thus, the fuel pressurization chamber 14 is blocked from fluidcommunication with the fuel supply line 30 by the check valve 32. Thepressure caused by the trapped gas acting on the opening hydraulicsurface 21 within the nozzle supply passage 15 is not great enough toopen the needle valve member 20. Thus, the nozzle supply passage 15 isblocked from fluid communication with the nozzle outlet 17. The plunger13 will advance downward to pressurize the fuel, but there will be nofuel within the fuel pressurization chamber 14 because the fuelpressurization chamber 14 is blocked from the fuel supply line 30 by theclosed check valve 32. The gas can never reach a high enough pressure toopen the direct needle control valve member 20 and the gas pressurenever drops low enough to allow the check valve 32 to lift to its openposition to allow fuel into the fuel pressurization chamber 14. Theplunger 13 reciprocates up and down but nothing happens with the fuelinjector 10. While this gas trapping exists in the prior art, it iseliminated in the present invention. Because the movement of the reverseflow valve member 160 is controlled by pressure within the fuelpressurization chamber 114, the pressure caused by gases that travelinto the fuel pressurization chamber 114 will act on the openinghydraulic surface 164 and move the reverse flow valve member 160 to itsopen position. The gases will flow through the groove 153 and into thenozzle supply passage 115. Thus, even if gases travel into the fuelpressurization chamber 114, they will not accumulate and be trapped.

[0040] If gases, other than combustion gases, become trapped within thefuel pressurization chamber 114 of a new fuel injector during assembly,the present invention also includes a priming feature that pushes thegas through the fuel injector 110 and out the nozzle outlet 17. Thepressure caused by the gases will act on the opening hydraulic surface164 of the reverse flow valve member 160 causing the reverse flow valvemember 160 to move downward against the action of the compressed spring161 and open fluid communication between the fuel pressurization chamber114 and the lower portion of the nozzle supply passage 115. When theplunger 13 advances, it will push the gases through the groove 153 andinto the lower portion of the nozzle supply passage 115. If there isstill gas within the fuel pressurization chamber 114 sufficient to keepthe check valve 32 in its closed position when the plunger 13 retractsto its upward position, fuel will not flow into the fuel pressurizationchamber 114 from the fuel tank (not shown). However, the plunger 13 willagain be hydraulically activated to move downwards against the action ofits biasing spring 16 and increase the pressure within the fuelpressurization chamber 114. The gases will again act on the openinghydraulic surface 164 of the reverse flow control valve member 160 andopen fluid communication between the fuel pressurization chamber 114 andthe lower portion of the nozzle supply passage 115. The gases will onceagain be pushed through the groove 153 and into the nozzle supplypassage 115. The reciprocating plunger 13 will continue pushing thegases out of the fuel pressurization chamber 114 into the lower portionof the nozzle supply passage 115 until the pressure within the fuelpressurization chamber 114 is low enough to allow the check valve 32 toopen. Fuel can then flow from the fuel tank (not shown) to the fuelpressurization chamber 114 via the fuel supply line 130 past the checkvalve. As fuel flows in, repeated plunger movements will eventuallyachieve needle valve opening pressure allowing the compressed gas andthe fuel to exit via the nozzle outlet 17. Thus, the present inventionnot only prevents gas trapping within the fuel pressurization chamber114 by blocking fluid communication between the lower portion of thenozzle supply passage 115 and the fuel pressurization chamber 114, thepresent invention also allows fuel injector 110 to prime itself if gastrapping does occur within the fuel pressurization chamber 114.

[0041] Referring to FIGS. 5 through 8, there is shown sectioned sidediagrammatic illustrations and top views of the reverse flow valvemembers 260, 360 according to the two alternate versions of the presentinvention. The reverse flow valve member 260, 360 according to thealternate versions of the present invention perform in the same manneras the reverse flow valve member 160 according to the preferredembodiment of the present invention. The difference between the threeembodiments are the shapes of the reverse flow valve members 160, 260,360 and the shape of the valve seats 163, 263, 363. For a discussion onthese differences, see the Detailed Discussion section of thisApplication.

[0042] Both the prior art and the present invention limit the trappingof combustion gases within the fuel pressurization chambers 14, 114 byblocking fluid communication between the nozzle supply passage 15, 115and the fuel pressurization chamber 114. However, unlike the prior art,in the event that gases, other than combustion gasses, are trappedwithin the fuel pressurization chamber 114 of a new fuel injector 110,the present invention can prime itself by pushing the gases out of thefuel pressurization chamber 114 and decreasing the pressure such thatthe check valve 32 can lift and allow fuel to flow into the fuelpressurization chamber 114. Also, this priming feature will eliminatethe need for the fuel injector 110 to re-prime itself because any gasthat travels into the fuel pressurization chamber 114 should eventuallybe pushed out of the chamber 114 by the downward strokes of the plunger13. Moreover, unlike the prior art in which the reverse flow check 52may not stay closed during the entire non-injection event, the reverseflow control valve member 160 of the present invention will remainclosed during the entire non-injection event. Therefore, the presentinvention does not just reduce, but prevents, gas trapping in the fuelpressurization chamber 114 caused by gas ingestion in the injector tip.Any gases that are ingested through the tip of the fuel injector 110will always remain in the portion of the nozzle supply passage 115 belowthe reverse flow valve member 160. The present invention removes theplate 50 from between the stop component 142 and the barrel 133. Thus,the seal between the stop component 142 and the barrel 133 is improvedand should reduce oil to fuel transfer. Moreover, the removal of theplate 50 eliminates the potential for excessive wear and plate breakageover time.

[0043] It should be understood that the above description is intendedfor illustrative purposes only, and is not intended to limit the scopeof the present invention in any way. Thus, those skilled in the art willappreciate that other aspects, objects, and advantages of the inventioncan be obtained from a study of the drawings, the disclosure and theappended claims.

What is claimed is:
 1. A fuel injector comprising: an injector bodydefining a nozzle supply passage and a nozzle outlet; a reverse flowvalve member positioned in the injector body and including an openinghydraulic surface exposed to fluid pressure in an upper portion of thenozzle supply passage, and being moveable between a closed position inwhich the nozzle supply passage is blocked, and an open position inwhich the nozzle supply passage is open; and a compressed springoperably positioned to bias the reverse flow valve member toward theclosed position.
 2. The fuel injector of claim 1 wherein the reverseflow valve member being movable along a line parallel to a centerline ofthe injector body.
 3. The fuel injector of claim 2 wherein the line isoffset a distance from the centerline of the injector body.
 4. The fuelinjector of claim 1 wherein the injector body includes a valve seat; thereverse flow valve member being in contact with the valve seat when inthe closed position, but out of contact when in open position.
 5. Thefuel injector of claim 4 wherein the valve seat is a flat valve seat. 6.The fuel injector of claim 1 wherein the injector body defines a guidebore; the reverse flow valve member being positioned in the guide boreand having a guide clearance in the guide bore.
 7. The fuel injector ofclaim 6 including an interaction between the reverse flow valve memberand the injector body, and being operable to prevent the reverse flowvalve member from rotating with respect to the injector body.
 8. Thefuel injector of claim 7 wherein the interaction includes a pin incontact with the injector body and the reverse flow valve member.
 9. Thefuel injector of claim I wherein the reverse flow valve member defines agroove that fluidly connects an upstream portion of the nozzle supplypassage to a downstream portion of the nozzle supply passage when in theopen position.
 10. A fuel injector comprising: an injector body defininga nozzle outlet and including a barrel in contact with a stop component;a reverse flow valve member trapped between the barrel and the stopcomponent, and being movable between a first position and a secondposition; a movable plunger at least partially positioned in the barrel;a nozzle supply passage, which includes a fuel pressurization chamber,being defined by the injector body, the plunger and the reverse flowvalve member; the fuel pressurization chamber being fluidly connected toa lower portion of the nozzle supply passage when the reverse flow valvemember is in the second position; a compressed spring operablypositioned in the injector body to bias the reverse flow valve membertoward the first position, in which the fuel pressurization chamber isblocked from the lower portion of the nozzle supply passage.
 11. Thefuel injector of claim 10 includes a nozzle outlet valve member with astop surface, and being moveable between a closed position in which thenozzle outlet is closed, and an open position in which the nozzle outletis open and the stop surface is in contact with the stop component. 12.The fuel injector of claim 10 wherein the barrel includes a valve seat;the reverse flow valve member being in contact with the valve seat whenin the first position.
 13. The fuel injector of claim 12 wherein thereverse flow valve member being moveable along a line parallel to acenterline of the plunger.
 14. The fuel injector of claim 13 wherein thereverse flow valve member defines a groove that fluidly connects theplunger bore to the nozzle supply passage when in the second position.15. The fuel injector of claim 13 including an interaction between thereverse flow valve member and the injector body, and being operable toprevent the reverse flow valve member from rotating with respect to theinjector body.
 16. The fuel injector of claim 15 wherein the interactionincludes a pin in contact with the injector body and the reverse flowvalve member.
 17. A method of reducing gas ingestion in a fuel injector,comprising the step of: moving a reverse flow valve member at least inpart with a spring to a position that blocks a downstream portion of anozzle supply passage to an upstream portion of the nozzle supplypassage.
 18. The method of claim 17 wherein the moving step includes astep of moving the reverse flow valve member into contact with a barrel.19. The method of claim 18 wherein the moving step includes a step ofmoving a stop surface of the reverse flow valve member out of contactwith a stop component.
 20. The method of claim 19 includes a step ofmoving a nozzle outlet valve member to a closed position.